The Development of Fe-nodules surrounding biological material mediated by microorganisms

Yoshida, Hidekazu; Yamamoto, Koshi*; Amano, Yuki; Katsuta, Nagayoshi*; Hayashi, Toru*; Naganuma, Takeshi

Environmental Geology, 55(6), p.1363 - 1374, 2008/09

https://doi.org/10.1007/s00254-007-1087-x

Takashikozo is a phenomenon of Quaternary sediments in Japan. They are cylindrical Fe-oxyhydroxide nodules that form as plaques round plant roots. Structural features suggest that after the roots have decayed, the central space where the roots were situated acts as a flow path for oxidized water. Analysis of microbial 16S rDNA extracted from the nodules identified iron-oxidizing bacteria encrusted round the roots where they are the likely initiators of nodule formation. Geological history and nanofossil evidence suggest that these Fe-nodules may have been buried at a depth of up to several tens of meters for a least 100000 years in reducing Quaternary sediments. Thus Fe-oxyhydroxide nodules with water and rock by microbial mediation can persist under reducing conditions. The phenomenon is significant as an analogue of post-closure conditions in radioactive waste repositories, since it could influence nuclide migration.